Liner top squeeze plug below retrievable tool

ABSTRACT

AN ANNULAR LINER PLUG IS RELEASABLY MOUNTED ON THE LOWER END OF A WELL BORE CEMENTING STRING BY MEANS OF A BALL-TYPE RETAINING AND RELEASING DEVICE. A RELEASING PLUG IS PUMPED DOWN THE CEMENTING STRING, FOLLOWING THE CEMENT USE TO CEMENT A LINER WITHIN THE WELL BORE, AND FORCEABLY ENGAGES WITHIN SLIDABLE SOCKET MEMBER WITHIN THE ANNULAR LINER PLUG. HYDROSTATIC PRESSURE ON THE RELEASING PLUG RESULTS IN THE SHEARING OF AN ATTACHMENT MEANS CONNECTING THE SLIDABLE SOCKET WITH THE INTERIOR OF THE ANNULAR LINER PLUG. THE SOCKET MEMBER SLIDES DOWNWARD, UNDER THE FORCE OF THE RELEASING PLUG AND PERMITS THE BALL DEVICE TO OPERATE SO AS TO RELEASE THE ANNULAR LINER PLUG FROM THE CEMENTING STRING. THE LINER PLUG IS PUMPED DOWNWARD AND, ULTIMATELY, SEATS OVER THE LINER AT THE BOTTOM OF A WELL BORE. THE LINER PLUG OPERATES TO SEAL OFF AN ANNULAR GAP BETWEEN THE LINER TOP AND A SURROUNDING CASING. THE RELEASING PLUG, ENGAGED WITHIN THE SOCKET MEMBER OF THE ANNULAR LINER PLUG, NOW OPERATES TO SEAL OFF THE CEMENT BELOW THIS ASSEMBLY FROM THE FLUID DISPOSED ABOVE THIS ASSEMBLY. LATCHING MEANS MAY BE PROVIDED FOR RETAINING THE RELEASING PLUG WITHIN THE ANNULAR LINER PLUG AGAINST ABRUPT BACK PRESSURES OR WELL &#34;KICKING.&#34;

. sept 20 1971 L. E. PERKINS 3,605,896

LINER TOP SQUEEZE PLUG BELOW RETRIEVABLE TOOL Filed June 4. 1969 2Sheets-Sheet 1 Sept. '20, 1911 3,605,896

LINR TOP SAOUEEZE PLUG BELOW RETRIEVABLE TOOL Filed June 4, 1969 L. E.PERKINS 2 Sheets-Sheet 2 INVENTOR 'LEE E. PERKINS vm v om BY Burns, bowwm',

Sweater i M11 n .N ma

United States Patent O U.S. Cl. 166-290 10 Claims ABSTRACT F THEDISCLOSURE An annular liner plug is releasably mounted on the lower endof a well bore cementing string by meansof a ball-type retaining andreleasing device. A releasing plug is pumped down the cementing string,following the cement used to cement a liner within the well bore, andforceably engages within slidable socket member within the annular linerplug. Hydrostatic pressure on the releasing plug results in the shearingof an attachment means connecting the slidable socket with the interiorof the annular liner plug. The socket member slides downward, under theforce of the releasing plug and permits the ball device to operate so asto release the annular liner plug from the cementing string.

The liner plug is pumped downward and, ultimately, seats over the linerat the bottom of a well bore. The liner plug operates to seal off anannular gap between the liner top and a surrounding casing. Thereleasing plug, engaged within the socket member of the annular linerplug, now operates to seal off the cement below this assembly from thefluid disposed above this assembly. Latching means may be provided forretaining the releasing plug within the annular liner plug againstabrupt back pressures or well kicking This invention relates to oil wellcementing and completion techniques, and more particularly to techniquesfor cementing the top of a liner disposed within the lower portion of acasing at the bottom of a well bore.

Squeeze cementing has, for some time, been a common type of wellcementing operation. The process involves applying hydrostatic pressureto force, or squeeze, a cement slurry into a formation through an openhole or through perforations formed in the casing. Engineers often findit desirable to squeeze cement liner tops which are axially overlappedby a casing.

Since cement slurry is not a true fluid, cement cannot be directlypumped into the interstices of many formations under a constant pressurewithout an undesirable amount of fluid loss. To cope with thissituation, a hesitation squeeze process has been developed and iscommonly employed. This method divides the squeeze cementing operationinto pumping and Waiting periods in order to control the fluid loss fromthe slurry. It has been found that such a method properly results in thebuilding of filter cake nodes on the formation while the parent slurry,within the casing, remains in a `fluid state.

When squeeze cementing is conducted in the zone Surrounding the top of aliner, however, additional problems are raised. These problems areaggravated by the use of the hesitation method but are offset by thepresent invention.

Essentially, the environment of the invention includes a liner conduitwhich is positioned at the bottom of a well bore. A well casing, with adiameter greater than the diameter of the liner, is fitted along thelength of the well bore so as to extend down to the upper end of theliner and to overlap therewith to form an annular space. When squeezecementing in the zone adjacent the overlap, with the hesitation method,the cement slurry dis- "ice i posed within the annular space and withinthe liner may be pressurized and displaced by hydrostatic fluid which isdirected into the well bore immediately above the cement and used todevelop the squeeze pressure.

When squeeze cementing, there may be a tendency for the mud followingthe cement to channel axially through a filter cake wall and thus fillthe casing-liner overlap with mud rather than cement.

lf the well bore should deviate from the vertical to any appreciabledegree, the displacing fluid may tend to overdisplace the cement slurry,i.e. channel between the Cement and the upper side of the deviatedcasing. This overdisplacement results in a condition where a hydrostaticfluid, such as mud, may occupy the annular overlap space instead ofcement slurry.

Another problem, which may be encountered, arises where the formationwill not support the hydrostatic head developed by the hydrostatic fluidafter the hydrostatic fluid has been pumped into the formation. In thissituation, the cement slurry is syphoned out of the annular space due tothe continuous fluid flow so as to result in a defective cementing job.

-Due to the cementing defects caused by the above discussed problems,cementing jobs may have to be repeated two or three times before asatisfactory job is attained.

Therefore, it would be advantageous to develop a method and apparatusfor cementing a liner, which apparatus and method would preventchanneling of mud into the overlap, prevent the overdisplacement ofcement slurry within a well bore having a deviation from vertical, dueto the overriding of a light hydrostatic fluid, and prevent thesyphoning of cement slurry from the annular space in the overlap betweenthe liner top and a surrounding casing.

OBJECTS AND SUMMARY OF INVENTION It is therefore an object of thepresent invention to provide an apparatus and a method for efficientlysqueeze cementing the top of well liners so as to obviate or minimizeproblems of the type noted above.

It is another object of the present invention to provide an apparatusand a method for cementing the top of liners without permitting mudchanneling of the column of cement disposed within the liner.

It is a further object of the present invention to provide an apparatusand a method for cementing liners within a well bore, which apparatusand method are simple and may be operated and performed using existingequipment requiring only minor adaptations.

It is still a further object of the presentinvention lt0 provide anapparatus and method for cementing the top of well liners, using thehesitation type of squeeze cementing, while offsetting the possibilityof overdisplacing the cement with mnd or cement displacing fluid.

It is yet another object of the present invention to provide anapparatus and a method for cementing liners in deviated wells whilepreventing cement displacing fluid from channeling into the liner-casingoverlap zone.

Briefly stated, the objects of the invention are carried out byproviding a cementing string with an annular liner plug which isreleasably secured to the bottom of the cementing string by attachmentmeans which release the annular liner plug in response to the impositionof a predetermined force on the annular liner plug. The releasing forceis provided by a releasing plug which is pumped down the cement string,engages the annular liner plug, seals a central channel defined by theannular liner plug, and cooperates with the annular liner plug to sealoil the top of the liner When the annular liner plug ultimately reachesa dinal position on top of the liner. The annular liner plug, itself,operates to seal off the annular gap between the liner and anoverlapping casing.

3 DRAWINGS While the invention is particularly pointed out anddistinctly claimed in the concluding portion of the specification, thepreferred embodiment may best be understood by reference to thefollowing detailed description taken in connection with accompanyingdrawings in which:

FIG. l is a cross-sectional view of a well bore having inserted thereinthe annular liner plug, of the present invention, detachably secured tothe lowermost portion of a cementing string;

FIG. 2 shows a cross-sectional view of the well bore of FIG. l whereinthe annular liner plug has been released and is being pumped in adownward direction;

FIG. 3 shows the lower portion of the well bore of FIG. 1 with theannular liner plug in a proper final position over the liner and sealingoff cement within the liner and within an annular gap or axial overlapbetween the liner and an overlapping casing;

FIG. 4 shows a releasing plug used to release the annular liner plugfrom a cementing string;

FIG. 5 is a detailed cross-sectioned, elevational view of the annularliner plug of the present invention;

FIG. 6 shows the annular liner plug of FIG. 5 with the releasing plug ofFIG. 4 forceably engaging therein so as to release a ball connectionbetween the annular liner plug and the lower portion of the cementingstring; and

FIG. 7 shows the annular liner plug with the releasing plug latchedtherein after separation of the annular liner plug from the lowermostportion of the cementing string.

GENERAL Referring now to the drawings in which like numerals are used toindicate like parts throughout the various views thereof, FIGS. l, 2 and3 show the overall apparatus assemblage of the preferred embodimentbeing operated within an oil well bore 11 in accordance with the presentinvention.

A casing is positioned within the well bore 11 formed within a formationmeans 12.. A conventional well liner 14 is inserted into the bottom ofthe well bore 11, with the upper portion 14a of the liner 14 generallyconcentrically overlapped by the lower portion 10a of the casing 10 soas to form an annular space 15 therebetween. The liner 14 and the casing10 generally comprise strong, non-corrosive metallic, cylindricalconduits. Liner 14 includes radial openings which may be slotlike orcircular in nature.

A cementing string 16 is provided with a packer member 20 at a lowermostend 17 thereof. The packer member 20 is of the selectively actuable typeused in testing, treating, and squeezing operations. Such packers areuseful for isolating zones along the length of a well bore in order thatcement may be forced into the formation at a particular permeable zoneby applying hydrostatic pressure to force, or squeeze, the cement intocontact with the formation. In this preferred embodiment, the packerused is the retrievable, test-treat, squeeze packer described on page 62of Halliburton Services Sales and Service `Catalog for 1968, HalliburtonServices, Duncan, Okla.

A cylindrical collar-like connector 22 is used to connect the lower endof the retrievable test-treat packer 20 with an annular liner plug 2'4.The attachment of the connector 22 with the annular liner plug 24 isdesigned to be releasable upon the applicable of a predeterminedmagnitude of uid generated force to the annular liner plug 24. Areleasing plug 26, pumped through the string 16 under the pressure of ahydrostatic substance, such as mud, carries out the operation ofapplying the sufiicient force to the annular liner plug 24 in order tocause the release of the liner plug 24 from the cylindrical collarlikeconnector 22. In the preferred embodiment, the latch down plug shown onpage 5l of the aforementioned Halliburton Services Sales and ServiceCatalog for 1968 was adapted for use as the releasing plug 26. The fourmembers comprising the cementing string 16, the packer 2,0, theconnector 22 and the plug 24 are all formed with axial passages 16a,20a, 22a and 24a, respectively, which are aligned for the passage ofcement slurry therethrough upon the conventional, threaded connection ofthe members.

In overall operation, the casing 1() and the liner 14 are conventionallypositioned within a well bore 11. The cementing string 16 is then ttedwith the retrievable test-treat squeeze packer 2,0 at the lower end 17of the string 16. The annular liner plug 24 is releasably attached .tothe retrievable test-treat squeeze packer 20` by means of thecollar-like cylindrical connector 22. The connection provided by themember 22, operatiing in combination with the retrievable test-treatsqueeze packer 20 and the annular line plug 24, is described in detaillater in the disclosure with reference to FIGS. 5, 6 and 7.

After connecting the cementing string 16, the packer 20, the connector22 and the annular liner plug 24 and after inserting this connectedassemblage within the casing 10, the packer 20 is set, i.e. expandedradially outwardly into sealing engagement with casing 10. Thereafter, amass or slug of cement is pumped through the axial passage, formed bythe connection of these members, and into the area adjacent the lowerend 10a of the casing 10. As the predetermined amount of cement ispumped into the casing 10 and into the liner 14 zone, the expandedpacker 20 insures that cement exiting from passage 24a ows downwardlytoward the liner 14 and into the annulus 15 between the liner 14 andcasing end 10a.

To terminate the liner, squeeze cementing operation, the releasing plug26 is placed in the axial passage 16a of the cementing string 16 whilethe last of the slug of cement is being directed into the well bore 11.Hydrostatic Huid, such as mud, is then directed, under pressure, intothe cementing string 16 immediately behind the releasing plug 26 andoperates to pump the releasing drill pipe plug 26 into forceableengagement with an upper portion of the annular line plug 24 so as torelease the plug 24 from the connector 22.

FIG. 2 shows the releasing drill pipe plug 26 in engagement with theannular liner plug 24 at a moment in time shortly after release of theannular liner plug 24 from the cylindrical, collar-like connector 22.The fluid surrounding the upper surfaces of the annular liner plug andthe releasing drill pipe plug comprises hydrostatic fluid such as mud Asis shown in FIG. 2, the annular liner plug 24 is driven down toward thetop 14a of the liner 14. The axial passage 24a, formed within theannular liner plug 24, is blocked olf by the releasing plug 26 after theplug 26 engages therein.

FIG. 3 shows the annular liner plug 24 resting in a proper finalposition over the well liner 14 and blocking the annular space 15between the liner 14 and the casing 10.

With this arrangement and technique, the Ihydrostatic iiuid followingthe cement will not tend to overdsplace the cement and occupy theannular space 15 between the liner 14 and the casing 10. Likewise, ifthe hesitation method should be used, the hydrostatic fluid will notchannel through the cement column below the annular liner plug 24. Thedrill pipe plug 26, engaged within the axial passage 24a of the linerplug 24, protects the column of cement within the liner 14 from anyfundesiralble effects of the hydrostatic uid. The seal provided by thecombined plugs 24 and 26 prevent a continued downward flow of fluidwhich might tend to siphon mud out of the space l5.

It should be understood that Ithe axis of the bore 11 may deviate asmuch as or more from the vertical.

When such is the case, overdisplacement of the cement by the lighterhydrostatic fluid along the upper portion of the casing is avoided.

Releasing plug FIG. 4 shows a detailed cross-sectional view of thereleasing plug 26 used to force the annular liner plug 24 out ofattachment with the cylindrical collar-like connector 22. The plug 26 isa composite unit, having a stem 3|() of drillable metal such as aluminumand a formed rubber plug body 32 which comprises four cuplike sections,each generally frustoconical in nature, and arranged one above theother.

The uppermost cup section 34 is deeper than the remaining cup sectionsand provides a greater inner surface area 35 upon which the pressure ofthe hydrostatic tluid may act. A rod-like nose member 36 is mounted on alower portion 30a of the stem 30` by means of female threads 38 machinedin an upper portion 36a of the nose member 36 and male threads 40 formedon a lower portion 30a of the stem 30x In order to ensure properisolation of tluid disposed below the releasa'ble plug 2.6 from uidabove the plug 26, a fluid seal 42 is provided and tits Within anannular groove 44 formed about the cylindrical periphery of the nosemember 36. At a lower end of the nose 36, a male threaded projection 46is formed and operates to retain a circumferentially and thus radiallycontractible split lock ring 48 and a. nose nut 50. The nose nut -`50holds the lock ring 48 in a position llush against a shoulder 52surrounding an upper portion of the threaded male projection 46. Thepurpose of the lock ring 48 is to latch the plug 26 within the annularliner plug 24 in a manner which will be explained later in thedisclosure in connection with FIG. )6 of the drawings.

The overall construction of the releasing plug 26 is a compact,composite unit which may be pumped through the axial passage I16a of thecementing spring 16 and through the contiguous passages a and 22a by theaction of the, hydrostatic fluid. The drill pipe plug travels down theoverall string until the nose 36 of the plug 26 engages within theannular liner plug 24 and is latched therein as mentioned above. Sincethe material comprising the releasing drill pipe plug is drillable, theplug may be left within the well Ibore 11 and the ditcult process ofretrieving the plug is thereby avoided.

Construction and operation of the annular liner plug FIG. 5 shows across-sectional view of the lower portion of the retrievable test-treatsqueeze packer 20; the connecting collar member 22, and the annularliner plug The connecting collar member 22 is secured to a lowerexternally threaded projection 52 of the retrievable testtreatingsqueeze packer 20 by means of internal threads S4 formed on the upperinside wall of the collar 22. Longitudinally extending andcircumferentially spaced slots 56 are formed as radial passages Withinthe collar 22 at the approximate midpoint along the axial length of thecollar 22.

Slots `56 permit a reverse circulation of uid in the FIG. l assembly,i.e. a vilow of fluid down annulius 10a, through slots 56, and uppassage means 20u to the wellhead.

The internally threaded wall portion of the collar 22 above the slots56, in a conventional manner, is slightly divergent, with respect to theouter wall, from the area defining the slots 5'6 to an upper end 58 ofthe collar 22. A shoulder 59 is formed on the lower end of the packer 20above and immediately adjacent the threaded projection 52. The upperinner wall of the collar 22 is formed with an annular recess -60` whichfits over the shoulder 59 of the packer 20. This overall connectionbetween members 20 and 221 provides strength against the loosenmginfluence of cyclic transverse forces acting on the collar 22 and theannular liner plug 24.

The inner wall of the collar connector 22, beneath the slotted area K56,is substantially parallel with respect to the cylindrical outer wallthereof, to a point midway between the slots 56 and a lower end 61 ofthe collar 22. At this midpoint, the inside diameter of the collarconnector is decreased so as to form a slight internal shoulder 62. Anannular recess 63 is grooved within the inner Iwall of the connector 22on the slight internal shoulder 62 midway along the axial lengththereof. The annular recess 63 is utilized to retain an O-ring seal 66which operates to preclude the leakage of fluid past the internalshoulder 62 when the collar connector member 22 is still connected withthe annular liner plug 24.

The overall annular liner plug 24- is provided with a hollow,cylindrical, stem-like mandrel 68, the upper end of which tits within alower end `61 of the connector member 22. A plurality of radial holes 70is drilled near the upper end of the mandrel 68 and a steel locking ball72 is placed within each radial hole 70. The diameter of each steel ballis somewhat larger than the thickness of the wall of the mandrel 68. Theoverall annular liner plug 24 includes an inner, hollow, socket orsleeve member 74 which is slidably mounted within the hollow, sternlikemandrel 68 and is connected thereto by means of a threaded brass shearscrew 76 which exhibits a low shear strength. The outer cylindrical wallof the slidable socket member 74 forces each steel ball 72 to projectslightly out of each hole 70l in the radially outward direction so as tobear upon the top of the shoulder 62 of the collar member 22 when theweight of plug 20 is vertically supported by the collar 22. In thismanner, the plug 24 is vertically supported within the collar 22 only bythe action of the balls 72. The weight of the plug 24 is transmitted tothe balls 72 by the surface dening the top of each hole 70 bearing uponthe top of each ball 72 and is transmitted to the collar 22 by the balls72, in turn, bearing upon the top of the internal shoulder 62 of collar22.

The socket member 74 is formed with a central axial passage 109 having acomposite configuration. The diameter of the passage 109 is increased atthe approximate midpoint of the axial extension thereof to form a recess75 therein. This recess 75 is used to latchably engage the lock ring 48of the drill pipe plug 26.

The hollow cylindrical mandrel 68 is threaded at a lower portion 78thereof and there engages with a complementary threaded portion 80 of ashoe member 82 which consists of a drillable metal. A rubber cup member84, which is annular in configuration, is positioned over the mandrel 68and rests upon the top surface 85 of the shoe 82. In order to adapt thecup member 84 for use with mandrels existing in the eld, an adaptor 86and a spacer 88 may be used to properly t the cup 84 with the mandrel 68and the shoe member 82.

The mandrel 68 is formed with an external shoulder 90 formed above thethreaded portion 78 thereof and the shoulder 90 engages within acomplemntary recess 92 formed on the inner wall of spacer member 88.When the shoe member 82 is tightly threaded on the mandrel 68, an outershoulder 94 of the spacer 88 presses a portion of the cup 84 against theadaptor member 86 and simultanously presses both the cup 84 and theadaptor member 86 down against the top surface 85 of the shoe member 82in order to form a composite, integral plug configuration.

An annular groove 95 and an O-ring seal 96 are provided on the insidesurface of the adaptor 86, to prevent the passage of lluid between theadaptor 86 and an outer surface of the spacer 88. A similar annulargroove 97 and an O-ring seal 98 are provided on the outer surface of themandrel 68 adjacent the spacer member 88 in order to prevent the passageof uid between the mandrel 68 and the spacer 88. An O-ring seal 99 andgroove 100 arrangement is also provided on the outer surface of theslidable socket member 74 to cooperate with an adjacent interior wall108 of the mandrel 68 and thereby to form a fluid tight sealtherebetween.

Radial ports 102 are formed in the mandrel 68 and in the slidable socketmember 74. The alignment of the ports 102 is such that, when the brassrod 76 is properly connecting the socket member 74 with the mandrelmember 68, there is a direct fluid communicating relationship betweenthe space surrounding the outside of the mandrel 68 and the axialpassage 109 inside the hollow slidable socket member 74. Since the axialspace 109 communicates with the space below the overall liner plug 24,equalization of pressure is effected between the spaces above and belowthe plug 24 before the drill pipe plug 26 is engaged within the linerplug 24.

This arrangement is especially useful for equalizing pressures whilerunning the overall apparatus into a well bore at operational speeds orfor reverse circulation around the packer if a squeeze pressure shoulddevelop before the liner plug 24 is released. Also, it may becomenecessary to retrieve the string from the bore with the plug 24 stillattached thereto and the provision of pressure equalizing slots 56 andports 102 prevents swabbing of the bore during such a retrieval.

Ports 102 and slots or ports 56 provide a continuously operable, reversecirculation system. If sleeve 74 should be moved downwardly, as shown inFIG. 6, to close port means 102, ports 56 will still provide a reversecirculation path. If plug 26 should engage sleeve 74 so as to block portmeans 56, but not move sleeve 74 downwardly, port means 102 would remainopen to permit reverse circulation.

An annular groove 104, which retains an outwardly expansible, split lockring 106, is formed in an outer surface 111 of the slidable socketmember 74. The lock ring 106 bears against the inside surface 108 of themandrel 68. This inside surface 108 is of substantially constantdiameter from the upper end 69 of the mandrel 68 to an internal recess110 formed just above the threaded area 78 of the mandrel 68. At thisrecess 110, the inside diameter of the mandrel 68 is increased for ashort axial distance beneath annular shoulder 116, and then decreasedfor another short axial distance at 112 before again being increased toform a second recess 114. The operational purpose of this compositeinner wall 108 configuration of the mandrel 68 may be best understood inconnection with FIG. 6.

FIG. 6 shows, in partial cross-section, the packer 20, the connectingcollar 22, the overall annular liner plug 24, and the releasing drillpipe plug 26 properly engaged Within the slidable, socket member 74 ofthe overall annular liner plug 24.

The releasing drill pipe plug 26 is pumped down through the cementingstring 16, through the retrievable test-treat squeeze packer 20 and intothe socket member 74. The nose portion 36 of the releasing drill pipeplug 26 fits within the slidable socket member 74 and passestherethrough until the lock ring 48 of the plug 26 engages within theinternal recess 75 of the socket 74 wherein the lock ring 48 expands inrecess 7411 and is retained by shoulder 74C. The lock ring 48 therebylatches the drill pipe plug 26 within the socket member 74 of theoverall annular liner plug 24. The socket member 74, being forceddownward within the hollow stem-like mandrel 68 by the forcetransmitting drill pipe plug 26, is, in turn, latched within the mandrel68 by the action of the socket member carried lock ring 106 expandingwithin recess 110 being retained by the shoulder 116 at the upper end ofthe internal annular recess 110 of the mandrel 68. This overall latcharrangement holds the plug 26 against any overriding reverse pressurewhich might result from kick back forces due to abrupt release of fluiddeposits into the bore 11 beneath the annular liner plug 24.

In this connection, it will be appreciated that as nose 36 enters sleeve74, resiliently expansible ring 48 will be contracted by sleeve cam 74aand then automatically re- 8 expanded adjacent sleeve wall 74b to belatched to sleeve 74 beneath sleeve shoulder 74C. Similarly, resilientlyexpansible ring 106 will expand in recess 110 to be latched to mandrel68 beneath shoulder 116.

Briefly summarizing the operation of the overall annular liner plug 24,the force of the releasing drill pipe plug 26 acting down on theslidable socket member 74, shears the brass rod 76 and causes theslidable socket member 74 to latch into a position clear of the areadefining the radial holes 70 which retain the steel balls 72. The steelballs no longer being confined to the radial holes 70, the slidablesocket member 74 may move downwardly and so the balls 72 may rollradially inwardly from the retaining holes 70 and into the interior ofthe stem-like mandrel 68.

As the steel balls 72 are removed from position, lthe connecton betweenthe collar 22 and the mandrel 68 is thereby also removed. Consequently,the overall annular liner plug 24, with the releasing drill pipe plug 26latched within the slidable socket 74 and blocking the central axialpassageway 109 therethrough, may drop away from the connecting collar 22as shown in FIG. 7. The pressure of the hydrostatic fluid above the plug24 then `may force the overall annular liner plug 24 into operationalposition on top of the liner 14 as shown in FIG. 3. The annular linerplug may now block off the annular space 15 between the casing 10 andthe liner 14. The column of cement within the liner 14 is similarlyprotected by the drill pipe plug 26.

SUMMARY OF ADVANTAGES AND SCOPE OF INVENTION A principal advantage ofthe invention resides in the provision of plug means for preventing thechanneling of mud, or other cement displacing fluid, into an annularzone which is desired to be cemented.

The invention is particularly advantageous when applied to the cementingof the annular zone between a liner conduit and a previously installedwell casing.

The utilization of the liner plug in conjunction with cementingoperations conducted in deviated wells is particularly significant inthat the plug offsets the normal tendency of the cement displacing fluidto channel past the top of the cement on the upper side of the Well.

The latching of the releasing plug to the actuating fluid or sleeve, andthe latching of this sleeve to the body of the liner plug provides asignificant locking arrangement tending to offset problems that mightdevelop during the liner plug releasing operation, if sudden pressureshould be generated beneath the cementing tool.

The circulating port arrangement provides a continuously effectivesystem for inducing reverse circulation operations if such should becomenecessary.

As will be recognized, the invention may be practiced while employingliner plug and releasing plug arrangements significantly different fromthose described in detail. Changes in plug seal structures, plug bodystructures, releasing and latching mechanisms, and overall plugconfigurations are well within the purview of the invention.

Changes of these natures as well as yother substitutions, modificationsand deletions are deemed to fall within the purview of this invention asdefined in the appended claims.

I claim:

1. Apparatus for cementing well conduits, comprising:

(a) a cementing string having a cementing packer positioned at a lowerend of said cementing string;

(b) an elongated annular plug having a mandrel `on one end and a plugbody on the other end, said mandrel having a slidable socket memberdisposed therein;

(c) a releasing plug;

(d) means for releasably mounting said annular plug to a lower end ofsaid packer; and

(e) said means for releasably mounting said annular plug to a lower endof said packer being 'operable to release said annular plug from thelower end of said packer in response to a forced engagement of saidreleasing plug witin said annular plug.

2. Well production apparatus comprising:

(a) a well bore;

(b) a well liner disposed within a lower end of said well bore;

(c) a well casing having a diameter greater than the diameter of saidwell liner and disposed along a substantial length of said bore;

(d) said well casing axially overlapping said well liner so to define anannular space therebetween;

(e) a cementing string inserted in said well bore;

(f) said cementing string being adapted for connection with a source ofcement slurry;

(g) an annular liner plug;

(h) a releasing plug;

(i) means for releasably securing said annular liner plug to a lower endof said cementing string; and

(j) said means for releasably securing said annular liner plug to alower end of said cementing string being operable to release saidannular liner plug from the lower end of said cementing string inresponse to a forced engagement of said releasing plug within saidannular liner plug; and

(k) said annular liner plug being operable to cover the annular spacebetween said casing and said liner upon release of said annular linerplug from said cementing string.

3. Cementing apparatus comprising:

(a) a mandrel having a hollow cylindrical wall, said wall formed todefine at least one radial hole;

(b) a ball disposed in each of said at least one hole, each said ballhaving a diameter greater than the thickness of said cylindrical `wallof said mandrel;

(c) an annular plug body mounted on a lower end of said mandrel;

(d) a hollow slidable socket member releasably secured by fasteningmeans within said mandrel, said lmember being so disposed within saidmandrel as to cover each said at least one hole and to retain each saidball from moving radially inward;

(e) said fastening means being releasable in response to the impositionof a predetermined magnitude of force on said slidable socket member.

4. In an apparatus according to claim 3 wherein said mandrel isconnected with a lower end of a cement string, the addition of:

(a) a hollow cylindrical connector member;

(b) said hollow cylindrical connector member being connected at an upperaxial end with a lower end of said cementing string;

(c) a lower axial end of said hollow cylindrical connector member beingsecured about the upper axial end of said mandrel so as to prevent eachsaid ball from moving radially outward from each said at least one hole;

(d) shoulder means formed on an inside surface of said hollowcylindrical connector and bearing on an underside of each said ball fortransmitting the weight of said hollow mandrel, said annular plug body,and said slidable socket member, to said hollow cylindrical connector;

(e) said shoulder means disengaging each said ball in response to areleasing of said fastening means and a predetermined axial movement ofsaid slidable socket member away from said at least one hole wherebyeach said ball moves radially inward and out of engagement with saidshoulder means.

5. An apparatus according to claim 4 wherein said hollow cylindricalconnector member is formed with at least one radial opening whereby uidmay be circulated between an outer surface of said hollow cylindricalconnector member and a hollow inner passage thereof.

6. An apparatus according to claim 3 with the addition of latch meansfor preventing axial movement of said slidable socket within saidmandrel upon the sliding of said slidable socket a predetermined axialdistance within said mandrel.

7. An apparatus according to claim 6 wherein said latch means comprises:

(a) an annular recess formed in an inner surface of said cylindricalwall of said hollow mandrel adjacent the lower end thereof, and

(b) lock ring means on said slidable socket member operable to lockinglyengage said annular recess.

8. An apparatus according to claim 7 wherein (a) said hollow mandrel andsaid slidable sleeve member are formed to define radial ports extendingentirely through said slidable sleeve member and said mandrel; and

(b) said radial ports are aligned so as to place the outer surface ofsaid mandrel in fluid pressure communication relationship with the innersurface of said slidable socket member upon attachment of said slidablesocket member within said mandrel by said fastening means.

9. A method for cementing a well liner to a well casing comprising thesteps of:

(a) providing a cementing string;

(b) releasably mounting an annular liner plug on a lower end of thecementing string;

(c) inserting the string and plug into the well casing;

(d) pumping a quantity of cement slurry through the cementing string andannular liner plug into the liner;

(e) placing a releasing plug generally adjacent the end of the cementslurry;

(f) pumping the releasing plug through the cement string and intoengagement with the annular liner plug;

(g) releasing the annular liner plug from the cementing string inresponse to the engagement of the releasing plug with the annular linerplug; and

(h) pumping the annular liner plug with the releasing plug engagedtherein into a position on top of the well liner so as to block anannular space formed in the axial overlap between the liner and casing.

10. A method according to claim 9 with the additional step of latchingthe releasing plug within the annular liner plug.

References Cited UNITED STATES PATENTS 1,594,498 8/1926 Day 166290X2,738,011 3/1956 Mabry `166-290X 3,090,442 5/1963 Cochran et al.166-224X 3,231,020 1/1966 Greene 166-117X 3,364,996 1/1968 Brown166-208X FOREIGN PATENTS 1,183,039 12/1964 Germany 166-290 DAVID H.BROWN, Primary Examiner U.S. Cl. X.R. 166-15 4

